1. Field of the Invention
The present invention relates to an improved process for the preparation of trimethylchlorosilane, and, more especially, to the preparation of trimethylchlorosilane via redistribution between tetramethylsilane and dimethyldichlorosilane, such redistribution reaction being catalyzed by particulate aluminum chloride, advantageously aluminum chloride granules.
2. Description of the Prior Art
Redistribution reactions between tetraalkylsilanes and alkylchlorosilanes, either in the presence of hydrogensilanes, and with the aid, as catalysts, of aluminum chloride or related compounds (alkaline chloroaluminates, complexes between alkyl aluminum dihalides and alkaline halides) are very well known to this art.
Nonetheless, the conditions under which the aforenoted redistributions proceed are quite severe and militate against broad application thereof. Thus, certain of such redistributions require temperatures in excess of 150.degree. C. and pressures higher than 10 bars (compare U.S. Pat. No. 3,135,778), or even temperatures in excess of 250.degree. C., under either atmospheric pressure (French Pat. No. 1,089,575) or pressures in excess of 100 bars (French Pat. No. 1,264,256).
Certain others of such processes may be effected at lower temperatures and at atmospheric pressure. However, when operating under such experimental conditions, the chemical literature reflects that the redistribution must take place in the liquid phase (French Pat. No. 1,147,688), which implies the use of large space occupying apparatus having low productivity. These space requirements may be reduced (U.S. Pat. No.3,793,357) by conveying or charging the alkylsilanes to be redistributed, in the vapor state, into a reaction medium comprising solid aluminum chloride and liquid arylhalosilanes having boiling points higher than those of the alkylsilanes, but here too disadvantages may arise; in particular, serious risk of redistribution between the alkylsilanes and the alkylhalosilanes exists. Furthermore, it is always difficult to separate the aluminum chloride from the silanes wherein it is dispersed or dissolved.